The present invention relates to a worm mower for cutting stalk material of any kind utilizing a moving worm which turns at a high circumferential velocity.
Worm mowers that turn at high circumferential velocities feature rotating cutting devices which cut the material to be mowed in a free cut. Furthermore, worm mowers of this type can also discharge the cut material to the side or over the top.
The suggested prior art worm mowers proved to be inadequate due to their unsatisfactory cutting quality.
Worm mowers must be differentiated from spindle mowers, the cutting bars of which run either longitudinally or slightly inclined along the circumference, and operate jointly with a counter-cutting blade on the bottom. Mowers of this type are used for cutting lawn areas with short-stalked grass.
One reason that worm mowers are not particularly suited for mowing is that the worm bends the blades or leaves considerably to the side, thereby making cutting difficult and also leaving the stubble longer.
Furthermore, compared to cutting with a blade running parallel to the axis, when cutting with a worm, there is a reduction in cutting velocity u.sub.1 proportionate to the pitch of the worm. The number of revolutions of the worm must be increased accordingly in order to attain the cutting velocity required to cut through the stalk. Consequently, the construction is more elaborate in order to give the machine necessary stability.
The tangential sliding velocity u.sub.2 can practically, however, not yield a drawing cut, because the helicoid surface of the worm runs in a vertical direction to the shaft.
Moreover, for a number of mowing operations, it is desired that the cut material be deposited somehow.
The primary object of the present invention is to provide a worm mower that permits mowing in a free cut at a low as possible circumferential velocity of the worm, and that if required, permits depositing of the cut material in a swath by exploiting the axial discharge effect of the same worm.
A solution of this object in accordance with the present invention and its further embodiments is described in the claims hereto.
An element of the present invention is that the pitch of the mowing worm (.alpha.) is less than the angle of friction of the material to be cut; furthermore, along its circumference the mowing worm is provided with a continuous or stepped cutting surface, arranged parallel to or inclined toward the axis of the worm.
For the axial discharge of the material to be cut in a swath or into a shredder or simply to the side, a section of the circumference of the mowing worm may be covered with a hood over its entire width, which at the same time also assumes a safety function.
It is especially difficult, as is well-known, to cut fine, almost dead leaf and stalk material in a free cut. To do so requires high cutting velocities, so that in order to keep the number of revolutions relatively low, a blade stepped in the axial direction would have to be employed as the cutting worm. However, loose, wilted blades of grass and fine stalks can stick to such a stepped blade.
For this reason, the cutting steps are designed somewhat oblique in the inclined or axial-parallel running circumference of the worm in the preferred further embodiments of the invention.